The present invention relates in general to anti-skid devices for vehicles. More specifically, the present invention relates to a device that provides a rotatable member with links of chain, or other traction or friction increasing means, intended to be thrown sequentially under a wheel of a vehicle for increased traction between the wheel and the road surface. One device of the type generally described above is disclosed in U.S. Pat. No. 4,800,939 issued to Törnebäck. Another device of the type generally described above is disclosed in U.S. Pat. No. 7,118,130, issued Oct. 10, 2006 to Rosenbalm. Both of these U.S. patents are incorporated by reference herein in their entirety.
The Törnebäck device utilizes an inflatable bellows to extend the movable arm that includes the pulley. It is important to note that a supply source of air for the bellows is required in order for the Törnebäck device to be operable. A suitable supply of air is likely available with larger vehicles such as semi-tractor trailers. Smaller passenger vehicles such as SUVs and trucks are not likely to have a suitable air supply. Another consideration with smaller passenger vehicles of the type described is the available space within and/or beneath the frame for securing an anti-skid device in position.
As described in the '939 patent, devices of this kind typically include a pulley provided with strands or links of chain or some other friction increasing means for sequentially positioning the chain beneath the vehicle wheel between the wheel and the road surface. Devices of this kind are not as simple to construct as would appear from the principle itself. Chains, pulleys, and other supports are, to start with, subject to very substantial forces necessitating heavy duty construction. Furthermore, a relatively large movement is required to displace the chain carrying pulley between its working position in contact with the vehicle wheel and its operative stored or stowed position. To store the pulley is particularly troublesome since different cars and passenger vehicles have different available places for the pulley. Furthermore, the pulley should be sufficiently elevated so that the chains attached to the pulley or chain wheel do not drag on the ground as this causes the links of chain to be worn prematurely. A result of the above requirements and problems that need to be solved with automatic anti-skid devices of the type described is that they are comparatively costly to produce which in turn results in a number of individuals being reluctant to obtain these safety increasing aids.
The Rosenbalm device includes an anti-skid device for use in cooperation with a vehicle wheel for positioning a traction member beneath the vehicle wheel includes a frame assembly constructed and arranged to be attached to the vehicle, a swing arm pivotally connected to the frame, and an electric, linear actuator having an extendable shaft. The anti-skid device includes a double pivot link where one end is attached to the frame assembly and the opposite end is attached to the swing arm. The linear actuator is attached to a movable pressure plate and a biasing spring is positioned between the movable pressure plate and a back plate for applying and maintaining contact pressure of the traction wheel against the vehicle wheel. In the preferred embodiment, the traction member is a length of chain that is connected to the traction wheel for positioning between the vehicle wheel and the road surface.
While the Törnebäck and Rosenbalm devices represent a couple of design options for these type of tire chain devices, a further option is to use an electric drive motor (but not involving any linear actuator as in Rosenbalm) as part of the deployment structure. The use of a reversible, electric drive motor, properly sized and gear reduced, yields a more compact design without requiring any vehicle or accessory air supply and without requiring any type of linear actuator or solenoid or similar cylinder. The desirable spring-biased aspect of the '130 Rosenbalm patent would preferably still need to be provided, but in a different structural configuration. The presently disclosed structure, as described and illustrated herein, achieves a compact design configuration by the use of an electric drive motor. In addition, a worm and worm gear combination is used for low speed and power amplification in combination with a biasing spring arrangement and appropriate gear reduction. These components and systems are provided and integrated in a novel and unobvious manner.